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Spectrograph

This article should be merged with Spectrometer, Spectroscope

A spectrograph is an instrument that transforms an incoming time-domain waveform into a frequency-domain spectrum, or generally a sequence of such spectra. There are several kinds of machines referred to as spectrographs, depending on the precise nature of the waves.

In optics, a spectrograph separates incoming light according to its wavelength and records the resulting spectrum in some detector. It is a type of spectrometer and superseded the spectroscope for scientific applications.

In astronomy, spectrographs are widely used. These are installed at the focus of a telescope which may be either in a ground-based observatory or in a spacecraft.

The first spectrographs used photographic paper as the detector. The star spectral classification and discovery of the main sequence, Hubble's law and the Hubble sequence were all made with spectrographs that used photographic paper.

More recent spectrographs use electronic detectors, such as CCDs which can be used for both visible and UV light. The exact choice of detector depends on the wavelengths of light to be recorded.

In acoustics, a spectrograph converts a sound wave into a sound spectrogram. The first acoustic spectrograph was developed during World War II at Bell Telephone Laboratories, and was widely used in speech science , acoustic phonetics and audiology research, before eventually being superseded by digital signal processing techniques.

Last updated: 11-03-2004 04:09:10